Motor vehicle headlamps

ABSTRACT

A motor vehicle headlamp having a light filament for dipped lighting in which masking of the filament is effected to produce two symmetrical half planes of cutout and prisms in the headlamp glass serve to raise one of the half planes so that the planes are staggered in height and connected by an inclined segment.

United States Patent [191 Ricard MOTOR VEHICLE HEADLAMPS Inventor:Jacques Ricard, Fontenay-sous-Bois,

France Assignee: Cibie Projecteurs, Bobigny, France Filed: July 23, 1973Appl. No.: 381,555

[30] Foreign Application Priority Data May 14, 1970 France 70.17586 US.Cl 240/41.3, 240/41.4, 240/106.l Int. Cl. F2lv 13/04 Field of Search240/4l.4, 41.3, 41.35,

References Cited UNITED STATES PATENTS 11/1919 Foster et a1. 240/4l.4 R

[4 1 Dec. 31, 1974 1,430,580 10/1922 Old 240/41.4 R 1,916,514 7/1933Koubek... 240/4l.4 R 1,950,978 3/1934 Falge 240/4l.4 R 2,122,465 7/1938Graves 240/4l.4 R 2,142,964 l/l939 Godley 240/4l.4 R

Primary Examiner-Richard L. Moses Attorney, Agent, or Firm-Edward J.Brenner 9 Claims, 12 Drawing Figures PATENTED 1 197-4 3, 858.040

SHEET 2 0F 8 PRIOR ART PRIOR ART Fl'gJb PATENTED I 1974 3, 858,040

sum 30F 8 mwggnma 1 1974 3, 858.040

SHEET 7 UF 8 PATENTED [E63 1 I974 SHEET 8 BF 8 MOTOR VEHICLE HEADLAMPSThe present invention relates to the headlamps of motor vehicles.

The problem of obtaining a satisfactory dipped beam (lower beam) is arecognized problem in the manufacture of motor vehicle headlamps. US andEuropean regulations and norms specify the lightintensities admissibleat certain points of the beam. There can be mentioned, for example, thenorm l-l European Code (rule 8 of Geneva) and the SAE norm. The aim isto obtain a beam which lights the road in front of the vehicleadequately, without any danger of dazzling the driver of an oncomingvehicle. I

In order to do this, it has been the practice to bring about a cut-outof the dipped light beam emitted by each headlamp, this beam appearingessentially as limited by two half planes. These two half planes may behorizontal and symmetrically disposed preferably, however, for headlampsof a vehicle adapted for driving on the right-hand side of the road, oneuses a horizontal half plane to the left of the central axis ofillumination and an inclined half plane directed upwards to the right ofthe axis of illumination and from this axis.

As a general rule, in the prior art, the cut-out of the dipped beam isobtained by the choice of relative location of the dipped light filamentin relation to the parabolic reflector together with the use of maskingelements provided to serve as screen or shield between the filament andthe reflector. For a lamp with an axial dipped filament, it is customaryfor instance to use a substantially semicylindrical cup located belowand all around the axial filament, the edges of the cup, parallel to theaxis of the headlamp, defining the two half planes of cut-out (Frenchstandard N.F. R136 for a symmettis l qt tand-. 13: fqta a ym i out).FlG. la shows schematically the known prior art to obtain anasymmetrical cut-out limit, said cut-out limit appearing on a referencescreen S. On said figure, P is a headlamp having a glass A, F the axialfilament of its lamp, C the above mentioned cylindrical cup havinghorizontal edges e. In this case, both edges e are not in the samehorizontal plane. FIG. lb shows, with the same references how to obtaina symmetrical cut-out with a cup C having both its edges e in the samehorizontal level (French norm R 136-02).

With headlamps having a transverse filament, one also knows cut-outmeans to obtain symmetrical cutout of the lower beam (SAE 1579a).

The present invention aims to obtain a new cut-out for a dipped beam fora car headlamp, which satisfies in a particularly effective manner thestandards and regulations in force, and relates to an arrangement ofmeans making it possible to obtain it in a simple and effective manner.

The new cut-out according to the invention is characterized by twohorizontal half planes of cut-out connected by an inclined plane, namelya plane inclined at about 45 relative to the horizontal. The horizontalhalf plane constituting the cut-out of the left-hand part of the beam ispreferably slightly below the horizontal plane passing through the axisof the headlamp and its parabolic reflector. The right-hand, horizontalhalf plane constituting for the main part of the masking limit of theright-hand part of the beam is, preferably, substantially in thehorizontal plane passing through the axis of the headlamp.

Naturally, the details given above are for a headlamp adjusted fordriving on the right-hand side of the road. It would be necessary totranspose the words right" and left" for a car adjusted for driving onthe left.

In the following, in order to simplify the description, we will onlyconsider the case of driving on the right, without this being in any waylimiting.

According to the invention, in order to obtain the new, aforesaidcut-out on the one hand, there is associated with the headlamp cut-outmeans known per se for effecting a horizontal cut-out along twosymmetrical half planes of cut out.

on the other hand, there are provided in the path of the light rays ofthe dipped beam, in particular at the level of the headlamp glass, aplurality of small prismatic, deflection elements,-each of saidprismatic elements intersecting a small part of said dipped beam justbelow said second half plane of cut-out, said small part of said beamprojecting with respect to a reference screen a quadrangular imagehaving an upper inside corner and an upper horizontal boundary, saidplurality of prismatic elements including a series of stepped prismaticelements, each of said series of prismatic elements deflecting said partof said beam in a vertical direction and also in a transverse directionto translate said corner to coincide on said screen with an obliquesegment, all of said prismatic elements intersecting and deflectingdifferent parts of said dipped beam to create finally for said beam acentral cut-out limit surface approximating step-by-step-wise on saidscreen said oblique segment and a lateral horizontal limit surfacestaggered in height relative to said unchanged first half plane ofcut-out.

The location of the prismatic deflection elements, their number, theirgeometric orientation, their dimensions, are chosen depending on theresult to be obtained. These factors may vary in each particular case,but, however, following these general criteria in the case of an axialdipped filament, the location of the prismatic elements must be chosenon both sides of the horizontal plane of symmetry passing through theaxis of the reflector in the case of a transverse, dipped filament,i.e., perpendicular to the axis of the headlamp, the location of theelements is chosen in the vicinity of the axial plane of symmetry of theheadlamp in both cases, the number of prismatic elements is chosen to besufficiently great in order that the plane of connection between the twohorizontal half plane of cut-out is sufficiently clear In both casesalso, the dimension of the prismatic elements depends on a certainmaximum admissible tolerance, taking into account the variation of theaberration as one moves away from the axis of the headlamp.

Preferably, the prismatic elements are associated with the headlampglass, being advantageously moulded with it.

The prismatic regions thus defined are theoretically defined on theglass by arcs of circles centred on the axis of the headlamp. However,in practice simpler shapes are satisfactory and the regions may belimited in the shape by small rectangles or small trapeziums withparallel vertical sides in the case of an axial filament and parallelhorizontal sides in the case of a transverse filament.

The following description, referring to the accompanying drawings, givenas non-limiting examples, will make it easier to understand how theinvention may be realised.

In the accompanying drawings FIGS. la and 1b have already been presentedas prior art headlamp including cut-out means.

FIG. 1 is a representation on a reference screen of a dipped beamproduced according to the present invention.

FIGS. 2 and 3 show in a similar illustration, the creation of thecut-out by the effect of prismatic zones in a headlamp according to thepresent invention.

FIG. 4 shows, in front view, a headlamp according to the presentinvention with an axial filament in which a cut-out is produced by meansof prismatic zones.

FIG. 5 is a graph illustratingthe choice of prismatic zones for theheadlamp of FIG. 4.

FIG. 6 is an illustration in projection, as in FIGS. 1 to 3 showing theproduction of the cut-out in the case of the headlamp of FIG. 4.

FIG. 7 is a front view of a headlamp according to the present inventionwith a transverse filament showing the location of these prismatic zonesfor producing the cut-out.

FIG. 8 is an illustration, on a screen, similar to that of FIGS. 1, 2, 3and 6, showing the formation of the cut-out in the case of the headlightof FIG. 7.

FIGS. 9 and 10 are schematic illustrations of the invention forheadlamps having respectively an axial and a transverse light filament.

FIG. 1 shows, on a vertical screen located at 25m from the headlamp,perpendicular to its axis, the new type of cut-out which it is desiredto obtain. The point H indicates the intersection of the screen and thecentral, horizontal axis of the headlamp. The reference I corresponds toa length of 25 cm. The new cut-out is constituted by a left-hand halfplane AB located slightly below the axis of the headlamp, a half planeDC located substantially at the level of this axis, with an inclinedconnecting plane BD, preferably at an inclination of 45.

Referring now to FIGS. 2 and 3, the obtention of the new cut-out willnow be explained. Firstly, one creates in a known manner 2 symmetricalcut-out constituted by two horizontal half planes Cg and C,,

If one considers a small, individual zone of the reflector, this zonegives an image such as G I J K on the screen (FIG. 2) in which thesegment GI is on the righthand half plane Cd.

There corresponds to a small area of the mirror a small area on theglass and an image on the screen, both defined by the shape of the basicbeam reflected by the small area of the reflector mirror.

If there is interposed at the level of the glass in the path of the saidbasic beam-which has just formed an image G I J K a prism withadeflecting effect, a point such as G may be moved to a point G' locatedon the segment BD previously defined.

With a plurality of areas, for example, four areas GIIIJIKI GgIgJgKgG3I3J3K3 G4I4J4K4, there can thus be produced a plurality of imagedisplacements such that all the points G,G,G G occur at G',, G G;,, G,along the segment BD, the point G substantially coinciding with B, thepoint G, with D, and the displaced segment G, I, with the half plane ofcut-out DC.

There is thus produced (FIG. 3) the desired cut-out by approximation ofthe rectilinear shape BD by a stepped contour.

Since the general method of obtaining the cut-out has been defined,there will now be described two accurate examples showing thedetermination of the location and of the dimensions of the prismaticelements within the framework of the invention.

In a first example, we examine the case of a headlamp whose dippedfilament is axial.

In this case, and if we refer to the method of forming an imagedescribed in relation to FIG. 3, the horizontal limit GI is given, inknown manner, by a cup/masking element located around the filament thislimitation is thus perfectly well defined.

The limit K] is a little significance for determining the cut-out. Itdepends on the height of the said region.

The basic limit for the formation of the cut-out is the limit GK. Thedistance from the point G to the axis of the beam varies according tothe distance from the corresponding area of the reflector to the axis ofthe reflector. In order that the displacements of the image to beproduced are not too great, it would be necessary, in principle, tochoose the regions as near as possible to the axis of the reflector. Inpractice, however, one is limited by the presence of the openingprovided at the rear of the reflector for the passage of the lamp anddue to the fact that near to this aperture, the reflector often hasdeformations.

On the other hand, in order that the line GK is not blurred, it isnecessary to place oneself at a point on the mirror where the aberrationis practically constant.

In order to make the explanation still clearer, more details of theexample chosen are given, by stating that it is a parabolic reflectormirror having a parameter of 45mm.

FIG. 4 shows a headlamp with a rectangular aperture provided with such amirror. As previously, A designates its glass, F its light filament, andC its cup constituting the symmetrical cut-out means. The determinationand the location of the prismatic regions 1, 2, 3 and 4 located on itsglass will now be discussed.

In the following, in known manner, the z-axis represents the variationsin height, the y-axis, the variations in width, the x-axis thevariations in depth, these variations being indicated in hundredths of aradian of angular separation.

In the particular example chosen, i.e., with a mirror of 45mm parameter,the variation of the aberration as a function of the distance from theregion to the axis of the reflector is shown in FIG. 5. In order thatthe aberration is practically constant, one solution would be to choosethe location of the prismatic regions between the points S and S' of thecurve. Such a solution is, however, impossible in practice due to thefact that the proximity of the attachment aperture of the lamp tends todeform the corresponding region of the mirror. In practice, and as canbe seen in FIG. 5, the tolerance T which can be allowed in the positionof each point such as G, determines the width of the corresponding areas1, 2, 3, 4 at the level of the glass. In other words, areas 1, 2, 3, 4are chosen as having the same tolerance T as seen on FIG. 5. On FIG. 5,it can be seen that for a tolerance T of 0.2 percent (in hundredths of aradian) the region 1 extends between the radii of aperture 56 and 62mm,the region 2 between the radii of aperture 62 and 68mm, the region 3between the radii of aperture 68 and 76mm, the region 4 between theradii of aperture 76 and 85mm.

The limits of the regions at the level of the glass are theoreticallyarcs of circles concentric to the glass, but for reasons of simplifyingthe equipment, it is possible, as shown in FIG. 4 to provide theprismatic surfaces 1, 2, 3, 4 on the glass in the form of smallrectangles having the previously defined width limits in the transverseplane passing through the axis of the headlamp.

If we consider the regions 1, 2, 3, 4 thus defined, their outlinescorrespond to a series of images, the limits GK of which are representedin FIG. 6 (limits G K G K G K It is a question of ascertaining theprisms to be associated with the regions 1, 2, 3, 4 of the mirror inorder to cause the displacement of the images shown in FIG. 6 in orderthat the points G G G G move to G,, G',, G';,, G., to come into theplane of cut-out inclined at 45 BD previously defined.

It should be noted that the lines GK are not straight vertical lines butcurves which have the advantage of minimizing the stepped appearance ofthe inclined cutout.

The regions g g g g, of FIG. 6 are the useful parts of the initialregions G I J K In order that their heights are similar, one choosesinitial regions 1, 2, 3, 4 of different heights.

In the example chosen, the region 1 and 2 are mm above the axis of theregions 3 and 4 are 3mm above.

In order to pass from a point such as G to a point such as G in eachprocess of forming an image, the displacements in width and in heightare the following Lateral Vertical Displacement Displacement From G to G0.5 1 From G to G 0.5 0.7 From G to G, 0.6 0.4 From G, to G, 0.6 0.2

The above displacements are made in hundredths of a radian of angularseparation relative to the headlamp, more precisely relative to theplane of its glass.

Under these conditions, the nature of the prismatic elements to beassociated with each of the regions of the glass is easily establishedas follows Line of the Greatest Angle slope relative to the 9 horizontalprism Region 1 65 115 Region 2 50 62' Region 3 38 50' Region 4 18 45 Wehave thus shown, by means of FIGS. 4, 5 and 6, the practical use of theinvention in the case of a headlamp with an axial filament, using anaccurate numerical example.

There will now be described by means of another example, and withreference to FIGS. 7 and 8, the use of the invention in the case of aheadlamp with a transverse filament (standard cut-out norm SAE J 579A).

In order to obtain horizontal images from a transverse filament, thereare used (FIG. 7) the regions 1, 2, 3, 4 which are substantially on thevertical axis of the headlamp.

In FIG. 8, the curves such as GK (i.e., G K Gl(,, G K,) represent aspreviously, the limits of the regions l, 2, 3, 4 which are chosen so asto be as near as possible to a cut-out of 45.

As previously, the points G G G are displaced to G',,, 6' 6' by means ofprismatic elements associated with each of the regions. The referencesused are the same as previously.

The accurate determination of the prismatic elements and of the regionsis within the scope of the man skilled in he art, taking into accountthe details which were given as regards the first example.

FIGS. 9 and 10 sum up schematically the teachings of the invention, forheadlamps P having known per se symmetrical cut-out means cooperatingwith an axial and a transverse filament, respectively.

One sees on a reference screen the above indicated formation ofquadrangular images 1 thanks to prismatic elements p.

It is to be understood that the number of regions is not necessarilyequal to 4 and that the shape of the cutout finally obtained is notnecessarily constituted by two horizontal half planes connected by asegment inclined at 45, other inclinations being possible withoutdeparting from the scope of the invention. Similarly, the regions on theglass may have any desirable optical shape in order to achieve this orthat particular cut-out effect, in particular for suppression orincreasing the stepped effect.

It should be understood that the prismatic elements which have beendescribed as preferably connected to certain regions of the glass couldjust as well be connected to homologous regions of the mirror, or tohomologus regions of an intermediate transverse plane located betweenthe reflector mirror and the glass, taking into account thecorrespondance which has been made explicit between a region of themirror, a region of the glass and an image region, all three located inthe same basic beam reflected by the reflector.

What is claimed is:

1. In a motor vehicle headlamp comprising a parabolic reflector adaptedto be mounted with a horizontal axis on a vehicle, a light filament fordipped lighting located in the vicinity of the focal point of saidreflector, a front glass, cut-out means for effecting cut-out of thedipped light beam according to a left and a right horizontal half planeof cut-out on either side of the central axis of said reflector and ofsaid headlamp, the improvement comprising a plurality of juxtaposed,prismatic elements, each of said prismatic elements inter secting asmall part of said dipped beam just below said right half plane ofcut-out, said small part of said beam projecting with respect to areference screen a quadragular image having an upper inside corner andan upper horizontal boundary, each of said series of prismatic elementsdeflecting said part of said beam in a vertical direction and also in atransverse direction to translate said corner to coincide on said screenwith an oblique segment, all of'said prismatic elements intersecting anddeflecting different parts of said dipped beam to create finally forsaid beam a central cut-out limit surface approximatingstep-by-step-wise on said screen said oblique segment and a lateralhorizontal limit surface staggered in height relative to said unchangedleft half plane of cut-out.

2. A headlamp according to claim 1, wherein the inclined oblique segmentis disposed at an angle of 45.

3. A headlamp according to claim 1, wherein the juxtaposed prismaticelements are molded with the front glass. t

4. A headlamp according to claim 2, wherein the filament is located onthe axis of the headlamp, the cut-out means comprise a masking cup withhorizontal edges, and the prismatic elements are located on the side ofthe from glass.

5. A headlamp according to claim 2, wherein the dipped filament islocated transversely relative to the axis of the headlamp and theprismatic elements are provided at the upper part of the glass in thevicinity of its vertical, axial plane.

6. A headlamp according to claim 1, wherein at least three prismaticelements are provided.

7. A headlamp accordirg to claim 3, wherein the dimension of eachprismatic element relative to the size of the glass is such that theoblique segment of cut-out has no noticeable blur.

8. A headlamp according to claim 3, wherein the prismatic elements aredelimited by trapezoidal shapes, the parallel sides of which arevertical in the case of an axial filament and horizontal in the case ofa transverse filament.

9. A headlamp according to claim 3 wherein the prismatic element aredelimited by rectangular shapes, the

parallel sides of which are vertical in the case of an axial filamentand horizontal in the case of a transverse

1. In a motor vehicle headlamp comprising a parabolic reflector adaptedto be mounted with a horizontal axis on a vehicle, a light filament fordipped lighting located in the vicinity of the focal point of saidreflector, a front glass, cut-out means for effecting cut-out of thedipped light beam according to a left and a right horizontal half planeof cut-out on either side of the central axis of said reflector and ofsaid headlamp, the improvement comprising a plurality of juxtaposed,prismatic elements, each of said prismatic elements intersecting a smallpart of said dipped beam just below said right half plane of cutout,said small part of said beam projecting with respect to a referencescreen a quadragular image having an upper inside corner and an upperhorizontal boundary, each of said series of prismatic elementsdeflecting said part of said beam in a vertical direction and also in atransverse direction to translate said corner to coincide on said screenwith an oblique segment, all of said prismatic elements intersecting anddeflecting different parts of said dipped beam to create finally forsaid beam a central cut-out limit surface approximating stepby-step-wiseon said screen said oblique segment and a lateral horizontal limitsurface staggered in height relative to said unchanged left half planeof cut-out.
 2. A headlamp according to claim 1, wherein the inclinedoblique segment is disposed at an angle of 45*.
 3. A headlamp accordingto claim 1, wherein the juxtaposed prismatic elements are molded withthe front glass.
 4. A headlamp according to claim 2, wherein thefilament is located on the axis of the headlamp, the cut-out meanscomprise a masking cup with horizontal edges, and the prismatic elementsare located on the side of the front glass.
 5. A headlamp according toclaim 2, wherein the dipped filament is located transversely relative tothe axis of the headlamp and the prismatic elements are provided at theupper part of the glass in the vicinity of its vertical, axial plane. 6.A headlamp according to claim 1, wherein at least three prismaticelements are provided.
 7. A headlmap according to claim 3, wherein thedimension of each prismatic element relative to the size of the glass issuch that the oblique segment of cut-out has no noticeable blur.
 8. Aheadlamp according to claim 3, wherein the prismatic elements aredelimited by trapezoidal shapes, the parallel sides of which arevertical in the case of an axial filament and horizontal in the case ofa transverse filament.
 9. A headlamp according to claim 3 wherein theprismatic element are delimited by rectangular shapes, the parallelsides of which are vertical in the case of an axial filament andhorizontal in the case of a transverse filament.